Distractable vertebral column and distracting tool

ABSTRACT

The subject matter of the present invention relates to an extendable spinal implant with a first outer sleeve and a second outer sleeve coaxially disposed thereto and an inside drive element which is connected by means of screws to at least one of the outer sleeves, with the inside drive element comprising a first thread, e.g., an outside thread, and with the outer sleeve that is connected by means of screws to the drive element comprising a second thread, e.g. an inside thread, that fits on the outside thread, with the inside drive element resting on a support ring and with the drive element being able to be driven in the area of its front surface that faces the supporting ring.

[0001] The subject matter of the present invention concerns an extendable spinal implant with a first outer sleeve and, coaxially disposed thereon, a second outer sleeve and an inside drive element which is partially connected by means of screws to at least one of the outer sleeves, with the inside drive element having a first screw thread, e.g., an outside screw thread, and the outer sleeve that is screwed to the drive element having a second screw thread, e.g., an inside screw thread, that fits on the outside screw thread.

[0002] Such spinal implants serve as intervertebral implants to replace individual vertebrae, as is known, e.g., from U.S. Pat. No. 4,657,550. In this prior-art intervertebral implant, a thread bolt is screwed into each end of a threaded sleeve, with the two front surfaces of the thread bolts facing away from each other meshing with the buttressing bases which abut the vertebrae to be buttressed. When the threaded sleeve is turned by means of a radially insertable pin or by means of a hooked wrench, the two thread bolts having a right-hand and a left-hand thread are screwed out of or into said threaded sleeve. The disadvantage is that the tool used for turning the threaded sleeve has to be removed and reinserted after it has made a certain turn, e.g., after a quarter turn, which is difficult or even impossible in a great number of surgical interventions.

[0003] Thus, the problem to be solved by the present invention is to make available a spinal implant, in particular an intervertebral implant, that can be more universally used and considerably more easily handled during implantation.

[0004] This problem is solved according to the present invention by means of an extendable spinal implant in which the inside drive element is resting on a supporting ring and the drive element can be driven in the area of the front surface that faces the supporting ring.

[0005] The inside drive element preferably has two inner sleeves. According to an advanced embodiment, each inner sleeve is screwed into an outer sleeve. The front surfaces of the inner sleeves that face each other preferably are resting on a supporting ring which spaces said sleeves a certain distance apart from each other.

[0006] In the spinal implant according to the present invention as claimed in Claim 1, the two outer portions are formed by an outer sleeve, which has the advantage that, compared to the prior art mentioned above, said outer sleeve supports the spinal implant over a larger supporting area on the facing vertebra. Thus, buttressing bases are not required. In addition, having the drive, in particular a bevel drive, located on the front surface makes it possible to avoid having to reinsert the tool after it has made a certain turn since the tool, in contrast to prior art, does not engage the circumference but the front surface of the drive element.

[0007] The drive element which is located between the two outer sleeves is preferably formed by two inner sleeves that are screwed into the two outer sleeves. The front surfaces of the inner sleeves that face each other rest on a supporting ring and are spaced a certain distance apart by means of said ring. The two inner sleeves can be driven in the area of their front surface, thus making it possible to screw them into and out of the outer sleeve. Since the two inner sleeves are spaced a certain distance apart, the two front surfaces can be accessed by means of the tool and can be turned without having to repeatedly reinsert the tool. This is a problem, e.g., with the prior art mentioned earlier as described in the U.S. Pat. No. 4,657,550 where the central element has to be turned by means of a pin or a hooked wrench.

[0008] An advanced embodiment provides for the front surface of the inner sleeve to have teeth, in particular, half of a pair of bevel teeth. By way of these teeth, the inner sleeve or the inner sleeves can be turned by means of a suitable tool, e.g., by means of the mating part of the bevel teeth, so as to carry out the screwing motion.

[0009] The supporting ring preferably has at least one radial opening. The opening serve to insert the tool into the supporting ring and to move it to the front surface of the inner sleeve, on the one hand, and to guide and support the tool, on the other hand. During surgical interventions, a guided and supported tool poses a much lower risk than an unguided and unsupported tool.

[0010] To hold and support the inner sleeves, the supporting ring according to the present invention has a shoulder which projects radially inwardly and which serves as a support for the front surface of the inner sleeve. This shoulder does not necessarily run along the entire circumference of the inside surface of the supporting ring, it suffices if enough segments are provided which support the sleeve and keep it from tipping over.

[0011] Another advanced embodiment provides for the opening and the shoulder to intersect with each other. When a tool is inserted through the opening into the supporting ring, this tool is located in the area of the shoulder and thus in the area in which the inner sleeve is buttressed so the front surface, i.e., the teeth of the inner sleeve, can be directly accessed.

[0012] A preferred variation provides for the diameter of the opening to be greater than the thickness of the shoulder. When a tool is inserted through this type of opening, it projects beyond the shoulder and can directly engage the front surface of the sleeve. When the sleeve is fitted with teeth, such as are provided in an advanced embodiment of this invention, the portion of the tool that projects beyond the shoulder directly mates with the teeth which project into the inside cross-section of the opening.

[0013] As already mentioned earlier, the teeth can be designed in the form of a bevel gear so that said bevel gear, in association with a mating tool, a toothed wheel gear system results. This has the significant advantage that, without the need of reinserting the tool, the inner sleeve can be very sensitively turned inside the outer sleeve, with any turning positions being possible. Thus, the inner sleeve does not have to be turned to a certain position in order to be able, e.g., to remove or reinsert the tool.

[0014] The inner sleeves and the outer sleeves preferably have a right-hand thread or a left-hand thread. This has the significant advantage that the same components can be used for the two inner sleeves; this also applies to the outer sleeves if no special adjustment to the position or shape of the vertebrae is necessary. Furthermore, only one tool or one machine setting is required to produce the inside thread on the outer sleeve and to produce the outside thread on the inner sleeve.

[0015] To ensure an optimum union between the implant and the surrounding tissue, the surface of the inner sleeves and/or the outer sleeves has perforations through which the growth of bone tissue is facilitated. In addition, the perforations also reduce the overall weight of the implant.

[0016] According to an advanced embodiment, at least one of the perforations of at least one of the sleeves is of a size that makes it possible to fill or to supplement the sleeve with tissue substance. After the spinal implant according to the present invention has been extended, this implant first must be filled with additional tissue substance which can easily be inserted via relatively large perforations. These relatively large perforations are also located in the surface of at least one of the sleeves, with the perforation preferably having an elongated or a long oval shape.

[0017] To ensure an optimum fit of the spinal implant to the curvature of the spinal column, at least one of the outer sleeves has a front surface which projects outwardly and which is located at an angle to the orthogonal plane relative to the longitudinal axis. Thus, this outside surface does not run perpendicular to the longitudinal axis of the spinal implant but is inclined relative to this plane. Since the system is a modular system, there are a number of different outer sleeves to choose from, which sleeves have outside surfaces with different angles of inclination or surfaces with no inclination.

[0018] These outside surfaces preferably have spinous extensions so that an optimum support on the abutting vertebra is ensured.

[0019] To fix the final extended position, the outer sleeve and the associated inner sleeve can be affixed to each other by means of a grub screw that can be radially screwed into the outer sleeve. This ensures that the spinal implant does not independently change its position, in particular that it does not contract.

[0020] To connect the two inner sleeves to each other, a locking element is provided, which locking element maintains the two inner sleeves on the supporting ring, with the locking element having outwardly projecting detents, in particular on elastic tabs, which extend behind inwardly projecting shoulders provided on the inner sleeve. An additional advantage of this locking element is that the entire spinal implant can be modularly constructed and can be assembled immediately prior to implantation. No tools are required since the locking element needs to be merely pushed into an inner sleeve and be extended behind the shoulders of the adjacent inner sleeve.

[0021] The subject matter of the present invention also relates to a tool for adjusting the extendable spinal implant, said tool being designed in the shape of a rod and having a star-shaped cross-section. In addition, the distal end of the tool can be slightly conically tapered similar to a beveled gear. The tool can be easily inserted into and turned in the supporting ring. In addition, the tool can be disposed on a flexible shaft so that the implant can be used and extended even if it is difficult to access the implant.

[0022] Other advantages, characteristics, and details of the invention follow from the description below which also includes details of an especially preferred embodiment which is described with reference to the drawing. The characteristics illustrated in the drawing and mentioned in the claims and in the description may be essential to the invention either separately or in any combination with each other.

[0023] The drawing shows the following figures:

[0024]FIG. 1: a perspective view of an embodiment of the extendable spinal implant according to the present invention;

[0025]FIG. 2: the spinal implant according to FIG. 1 in an extended position;

[0026]FIG. 3: the spinal implant according to FIG. 1 in an exposition [sic; exploded] view;

[0027]FIG. 4: an enlarged representation of a perspective view of the upper outer sleeve according to FIG. 3;

[0028]FIG. 5: an enlarged representation of a perspective view of the lower outer sleeve according to FIG. 3;

[0029]FIG. 6: an enlarged representation of a perspective view of an inner sleeve;

[0030]FIG. 7: a longitudinal section through the inner sleeve;

[0031]FIG. 8: an enlarged representation of a perspective view of a supporting ring;

[0032]FIG. 9: an enlarged representation of a perspective view of a locking element, and

[0033]FIG. 10: a perspective view of a tool for extending the spinal implant.

[0034]FIG. 1 shows a preferred embodiment of a spinal implant in its compressed state which in its entirety is designated as 10. One can see an upper outer sleeve 12 and a lower outer sleeve 14 which, with their front surfaces 16 (see FIG. 2) facing each other, rest against a supporting ring 18. In addition, one can see that outer sleeves 12 and 14 have perforations 20 through which bone tissue can grow into the inside of the spinal implant 10.

[0035] Supporting ring 18 has radially running openings 22, through the inside cross-section 24 of which portions of teeth 26 can be seen. Also, the two outer sleeves 12 and 14 have outwardly oriented front surfaces 28 and 30 which have spinous extensions 32 that project in an axial direction. These spinous extensions 32 penetrate the contact surfaces of the neighboring vertebrae and there anchor the two outer sleeves 12 and 14.

[0036]FIGS. 2 and 3 show an upper inner sleeve 34 and a lower inner sleeve 36 which are screwed into the associated upper outer sleeve 12 and lower outer sleeve 14. In addition, the figures show two grub screws 38 which can be screwed into an associated tapped hole 40 of outer sleeves 12 and 14, which affixes outer sleeves 12 and 14 to inner sleeves 34 and 36. Tapped holes 40 for grub screws 38 are located in the immediate vicinity of front surfaces 16 of outer sleeves 12 and 14. Also visible is a locking element 42 by means of which the two inner sleeves 34 and 36 can be attached to each other.

[0037] One can clearly see that the plane of front surface 28 is inclined at an angle α to the orthogonal plane relative to longitudinal axis 44. This makes it possible to optimally adjust spinal implant 10 to the position of the neighboring vertebrae or to correct the position of said vertebrae. For this purpose, an outer sleeve 12 or 14 having a front surface 28 or 30, respectively, with the inclination required is selected. It can also be seen that sleeves 12, 14, 34, and 36 and supporting ring 18 and locking element 42 are disposed coaxially with respect to one another and with respect to longitudinal axis 44.

[0038]FIGS. 4 and 5 are enlarged representations of the two outer sleeves 12 and 14, except that the inside thread 46 disposed on the inner circumference is only schematically shown or suggested. This inside thread 46 is, e.g., a fine thread with a pitch of 1 mm and a diameter of 22 mm, and is designed as a right-hand thread.

[0039]FIGS. 4 and 5 also show that a relatively large oblong perforation 48 is provided in the walls of outer sleeves 12 and 14, through which perforation, after extension, bone tissue can be filled into the inside of spinal implant 10.

[0040]FIG. 6 shows an enlarged perspective view of inner sleeves 34 and 36 which, along their outer circumference, have an outside thread 50 which again is only schematically shown or suggested. Inner sleeves 34 and 36 also have perforations 52. On one of their front surfaces 54, inner sleeves 34 and 36 have a flange 56 which projects radially outwardly and which, on its outwardly oriented front surface, has teeth 26 which are preferably designed in the form of beveled teeth. In the longitudinal section shown in FIG. 7, these beveled teeth can be clearly seen.

[0041] It can also be seen that flange 56 has a shoulder 58 which projects radially inwardly and onto which detents 60 of a locking element 62 can latch. Such a locking element 62 is shown in FIG. 9. This locking element 62 is also designed in the form of a sleeve and has, on its surface lying oppositely to detents 60, a radially projecting retention flange 64 which comes to lie behind the associated shoulder 58 of the other inner sleeve 36. The detents are disposed on elastic tabs 68, thus making it possible to deflect them radially toward the inside. In this manner, it is possible to connect the two inner sleeves 34 and 36 to each other.

[0042]FIG. 8 shows supporting ring 18 on which the two inner sleeves 34 and 36 with teeth 26 are seated. For this purpose, supporting ring 18 should have a shoulder 66 which projects radially inwardly and which is subdivided into a total of six segments. Shoulder 66 is disposed in such a way as to intersect with openings 22, with the diameter of openings 22 being greater than the thickness of shoulder 66. This has the effect that part of teeth 26 project into the inside cross-section of openings 22 when inner sleeves 34 and 36 are resting on shoulder 66. Teeth 26 can thus be accessed from the outside through opening 22, as shown in FIGS. 1 and 2.

[0043]FIG. 10 finally shows a tool 70 which has an oblong shape and a star-shaped cross-section. Tool 70 also has teeth 72 which, together with teeth 26, form a bevel tooth gear. The tool can be disposed on a rigid rod or on a flexible shaft, thus making it easily possible for tool 70 to reach even difficult-to-access areas and to extend spinal implant 10. 

1. An extendable spinal implant (10) with a first outer sleeve (12) and a second outer sleeve (14) coaxially disposed thereto and an inside drive element which is connected by means of screws to at least one of the outer sleeve (12,14), with said inside drive element having a first thread, e.g., an outside thread (50), and with the outer sleeve (12,14) that is connected by means of screws to the drive element having a second thread, e.g., an inside thread (46), that fits on the outside thread (50), characterized in that the inside drive element is seated on a supporting ring (18) and that the drive element can be driven in the area of its front surface (54) that faces the supporting ring (18).
 2. The spinal implant as claimed in one of the preceding claims, characterized in that the drive element comprises two inner sleeves (34 and 36).
 3. The spinal implant as claimed in claim 2, characterized in that each inner sleeve (34 and 36) is screwed into an outer sleeve (12 and 14).
 4. The spinal implant as claimed in claim 2 or 3, characterized in that the inner sleeves (34 and 36) are spaced a certain distance apart by means of the supporting ring (18).
 5. The spinal implant as claimed in any one of the preceding claims, characterized in that the front surface (54) of the drive element or the inner sleeve (34 and 36) has teeth (26).
 6. The spinal implant as claimed in any one of the preceding claims, characterized in that the supporting ring (18) has at least one radial opening (22).
 7. The spinal implant as claimed in any one of the preceding claims, characterized in that the supporting ring (18) has a shoulder (66) which projects radially inwardly and which serves as a support for the front surface (54) of the inner sleeve (34,36).
 8. The spinal implant as claimed in claims 6 and 7, characterized in that the opening (22) and the shoulder (66) intersect with each other.
 9. The spinal implant as claimed in claim 8, characterized in that the diameter of the opening (22) is greater than the thickness of the shoulder (66).
 10. The spinal implant as claimed in claims 5 and 6, characterized in that the teeth (26) project into the inside cross-section of the opening (22).
 11. The spinal implant as claimed in any one of the preceding claims, characterized in that each of the inner sleeves (34 and 36) and the outer sleeves (12 and 14) have a right-hand thread or a left-hand thread.
 12. The spinal implant as claimed in any one of the preceding claims, characterized in that the surfaces of the inner sleeves (34 and 36) and/or the outer sleeves (12 and 14) have perforations (20,48).
 13. The spinal implant as claimed in claim 12, characterized in that at least one of the perforations (48) of at least one sleeve (12,14,34 or 36) is large enough so as to make it possible to fill the sleeve (12,14,34 or 36) with tissue substance.
 14. The spinal implant as claimed in any one of the preceding claims, characterized in that one of the outer sleeves (12 or 14) has an outwardly projecting front surface (28) which is positioned at an angle (a) to the orthogonal plane relative to the longitudinal axis (44).
 15. The spinal implant as claimed in any of the preceding claims, characterized in that the outer sleeve (12,14) and the associated inner sleeve (34,36) can be affixed to each other by means of a grub screw (38) that can be radially screwed into the outer sleeve (12,14).
 16. The spinal implant as claimed in any one of the preceding claims, characterized in that the two inner sleeves (34 and 36) are maintained on the supporting ring (18) by means of a locking element (42), with said locking element (42) having outwardly projecting detents (60) which extend behind inwardly projecting shoulders (58) that are disposed on the inner sleeve (34,36).
 17. A tool (70) for adjusting an extendable spinal implant (10) as claimed in any one of the preceding claims, characterized in that the tool (70) is designed in the shape of a rod and has a star-shaped cross-section. 